Cadmium plating



Patented Aug. 1928.

UNITED STATES PATENT OFFICE.

LEON R. WESTBROOK, OF CLEVELAND, OHIO, ASSIGNOR TO THE GRASSELLI CHEMICAL, COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

CADMIUM PLATING.

No Drawing.

This invention relates to the electrodepo'sition of cadmium and to a process and a com position for that purpose.

As is known, deposits of cadmium upon other metals, for instance iron and steel, such as may be produced by electrodeposition, possess admirable protecting properties, but considerable difficulty has been encountered in devising [a satisfactory method for producing cadmium deposits having certain desired characteristics, as for example hardness and denseness. Among the difficulties encountered may be mentioned, also, the apparent inability to avoid producing dark deposits of cadmium when plating at current densities above about 10 to 15 amperes per sq. ft., even in the presence of an addition agent.

An object of theinvention is to provide a method whereby cadmium may be electroplated in the form of bright, hard, dense and smooth deposits at current densities up to and even exceeding 80 amperes per sq. ft.

The invention is based upon my discovery of the fact that under the influence of small amounts of certain metals in the cadmium plating solution, or bath, the above ob ect may be attained.

The invention more particularly relates to the addition of small amounts of nickel to a cadmium cyanide plating bath.

By applying this discovery, cadmium platings may be produced which are sufficiently hard and dense to withstand the ordinary buffing operation without detri ment thereto, and which even when produced at'current densities above those heretofore re arded as operative for the production of bright deposits, are of excellent brilliance and color surpassing those hitherto obtainable at lower current densities.

. Among those metals the presence of-Which in small amounts in the cadmium plating bath produces the above-mentioned effects are: nickel, cobalt and copper. In general I prefer to make use of those metals of the iron group having an atomic weight greater than 58. It has been found that the pres ence of a small amount of nickel is particularly effective in this connection, cadmium platings possessing some of the before-mentioned desirable characteristics having been produced in the presence of as little as 0.0001% of nickel, based on the weight of Application filed November 23, 1926. Serial No. 150,376.

the bath. For practical operations the nickel content of the bath should be at least 0.001%, and I prefer to use about 0.01 to 0.03%. The relative concentration of the added metal may vary within wide limits. For example, in the case of nickel, I have found that cadmium platings made from a double cyanide bath containing as much as 0.03% of nickel (based on the weight of the bath) have marked brilliance and denseness.

(Quantities of nickel equal to and even exceeding 0.10% of the weight of the bath hzwe been used with good results.

The effect of increasing ,amounts of the metal in the bath is to greatly broaden the band of current densities over which a bright cadmium plate may be dbtained. For ex ample, using 0.005% of nickel in the solu-- tion, bright platings may be secured up to 30 amperes per sq. 'ft. on the cathode, while equally bright platings maybe obtained at current densities up to 60 amperes per sq. ft.

contain no trace of that added metal, and in part an alloying effect, in that cadmium platings made from a bath containing relatively high amounts of the added metal have been found to contain a portion of the added metal in the form of an alloy. For example, in cadmium platings made from a double cyanide bath containing 0.03%. of nickel (based on the weight of the bath) there have been found small amounts of nickel in theform of a cadmium-nickel alloy. By the addition of larger amounts of the metal to the cadmium plating bath there may be obtained alloy deposits having various desirable characteristics.

That the efi'ect of the added metal may be in part catalytic may be still further substantiated by the observation that certain other metals, for example, arsenic, antimony, tin and thallium, appear to exert a detrimental effect in the cadmium plating bath, analogous to the poisoning effect of arsenic in other catalytic opcrations.-

The above-described characteristic effects are obtained by the addition of a small amount of the metal to any double cyanide cadmium solution, irrespective of its particular composition, and with or without the addition of ammonia or ammonium salts, caustic soda or sodium salts such as sodium sulfate. Preferably there may be 'Ewample 1 To a bath kgms. of cadmlum hydroxide, 2.6kgms. of sodium cyanide and 280 gms. of gulac in 20 liters of water, there is added 0.25 gm. of nickel as nickel cyanide, Cadmium platings obtained therefrom, at a current density of about 15 amperes per sq. ft., are bright, hard, dense and of good color.

Equally good platings may be obtained from the above solution at current densities up to about 60 amperes per sq. ft. by increasing the amount of the nickel there prescut to about 7.5 grams.

Good platings also may be obtained from the above solution by substituting for the nickel about from 12 to 35 grams of cobalt, in the form of a soluble salt thereof.

Example 2. p 1.134 kgms. of cadmium hydroxide arecombined with an amount of nickel hydroxfrom this-solution at current densities of from 15 to 60 amperes per sq. ft. are smooth,

hard and dense; capable of withstanding buffing operation and have a desirable brilliance and good color.

From ,the foregoing description it isa parent that the relative proportions of tiie constituents in the cadmium plating baths invention.

prepared by dissolving 1.2

For example, a dry mixture, suitable for shipment and storage, comprising all of the ingredients of the solution, less the necessary water, may be prepared. Or the electroplatcr may be supplied with a dry 'mixture (X uprising, for instance, cadmium hydroxide, the added metal, in the form of a compound thereof, and gulac with directions as to the quantity thereof to be dissolved in a given quantityof water along with sodium cyanide and, if desirable, sodium hydroxide, separatelysupplied.

The electroplating from cadmium plating baths containing small amounts of a suitable added metal may be carried out substantially as disclosed in U. S. Patent No. 1,564,413, to Clayton M. Hoff e. g., at room temperature using a potential of 4 to 6 volts, and preferably using cadmium anodes with an anode surface area equal to two or three times the cathode surface area. Known expedients such as agitation or circulation or heating or cooling of the bath,

rotation of the electrodes, etc., may be employed.

I claim: A

1. A cadmium plating bath for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, the essential metal components of which bath consist of a cadmium compound and a substantial predetermined small amount of a compound of a metal of the iron group having an atomic weight greater than 58. o

2. A cadmium plating bath for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, the essential metal components of which bathconsist of a cadmiumcompound and a substantial predetermined small amount. of acompound of nickel.

3. A cadmium plating bath for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, the essential metal components of which bath consist of a cadmium compound and a compound of nickel in an amount equal to about from 0.001% to 0.10% of the weight of said bath.

4. A cadmium plating bath for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, the essential metal components of which bath consist of a cadmium compound and acompound of nickel in an amount equal to about from 0.01% to 0.03% of the weight of-said bath. 5, As an electrolyte for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, an aqueous solution comprising a. compound of cadmium as the major metal component, a. cyanide and a substantial predetermined small amount of a compound of a metal of the iron group having-an atomic Weight greater than 58.

6. As an electrolyte for the electrodeposition of bright, hard, dense, smooth deposits- 1 a compound of cadmium as the major metal component, a cyanide and a substantial pre-, determined small amount of acompound of nickel. J

7. As an electrolyte for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, an aqueous solution comprising a compound of cadmium as the major metal component, a cyanide and about from 0.001% to 0.10% a compound of nickel based upon the weight of the solution.

8. As' an electrolyte for the electrodeposition of bright, hard, dense, smooth deposits of cadmium, an aqueous solution comprising a compound of cadmium as the major metal component, a cyanide, and about from 0.01% to 0.03% of a compound of nickel based upon the weight of the solution.

9. A cadmium plating bath for the electrodeposition of bright, hard, dense, smooth cadmium deposits, the essential metal components of which, bath consist of a cadmium compound and a relatively small amount of a compound of a metal of the group consisting of cobalt, nickel and copper.

10. As an electrolyte for the electro'deposition of bright, hard, dense, smooth cadmium deposits, an aqueous solution comprising a cadmium compound, a cyanide and a relatively' small amount of a compound of a metal of the group consisting of cobalt, nickel and cop er.

i 11. A cadmium plating composition comprising a cadmium compound and a relatively small amount of a brightening agent, said brightening agent being a com ound of a metal of the group consistlng of mckel, cobalt and copper, said metal compounds being soluble in an aqueous alkali metal-cyanide solution.

12. A cadmium plating composition comprising a cadmium compound and a rela-- tively small amount of a brightening agent, said brighten ug agent being a compound of a metal of the iron group having an atomic weight greater than 58, said metal compounds bein soluble in an aqueous alkali metal cyani e solution.

13. A cadmium plating composition .comprising cadmium hydroxide and a relatively small amount of a brightening agent, said bri htening agent being a nickel compound which is soluble in an aqueous alkali metal cyanide solution. a

14. A cadmium plating composition comprising cadmium hydroxide, an organic addit ion a ent, at least one additional electrolyte an brightening agent, said brightening agent being a nickel saltwhich is soluble in an aqueous alkali metal cyanide solution.

15. A cadmium platin composition comrising about 50 parts of cadmium hydroxide, about 0.18 part of nickel as a compound of nickel which is soluble inan aqueous alkali metal cyanide solution, about 38 parts of sodium sulfate and about 11.5 parts of gulac. 1

16. A cadmium plating composition comprising about 50 parts of cadmium hydroxide, about 0.18 part of nickel as nickel sulfate, about 38 parts of sodium sulfate, about 11.5 parts of gulac and about 100 parts of sodium cyanide.

In testimony whereof, I afiix my signature.

LEON R. WESTBROOK.

a relatively small amount of a. 

